Media kit: Suppress -Werror=class-memaccess

* Add media_format::Clear(), media_format::Unflatten().
* Replace memset() with media_format::Clear()
* Replace memcpy() with media_format::Unflatten()

Fix #14156

Change-Id: I38ebc2de4915b954a15b6f4f6b40d016506910e5

headers/os/media/MediaDefs.h

@@ -604,6 +604,9 @@ public:
 	const void*		MetaData() const;
 	int32			MetaDataSize() const;
 
+	void			Unflatten(const char *flatBuffer);
+	void			Clear();
+
 					media_format();
 					media_format(const media_format& other);
 					~media_format();